Well I found something similar...if you used Lizard (the installation wizard) it does not install a boot manager, so there is no way to directly boot to Linux. If you installed Linux from Windows (say from a CD-ROM) when you reboot, the computer will go back to Windows (or in your case, nothing) and you'll need to reinstall Linux.

You aren't entirely screwed if you have a Windows XP start-up disk, allowing you to go through DOS, to boot up Windows XP. Otherwise, you may just have to format the disk, and reinstall XP. I hope you backed up before you decided to install Linux!

i went to best buy today and got it fixed)
(i think i'm gonna wait until i get to college and after several months i'll attempt the dual operating system gig again... with the help of a 4th yr graduate student lol~!)

lol hey i just had the same problem a few days ago. i formated my system like 10 times trying to get it to work but i finally got it installed. what linux are you using? redhat's?? if you want help email me or post a reply. its not very hard.